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🛡️ CVE-2026-5545 — curl

🟡 CVSS 6.5 — Medium ⚠️ Exploit Public CWE-613 NVD
6.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

libcurl might in some circumstances reuse the wrong connection when asked to

do an authenticated HTTP(S) request after a Negotiate-authenticated one, when

both use the same host.

libcurl features a pool of recent connections so that subsequent requests can

reuse an existing connection to avoid overhead.

When reusing a connection a range of criteria must be met. Due to a logical

error in the code, a request that was issued by an application could

wrongfully reuse an existing connection to the same server that was

authenticated using different credentials.

An application that first uses Negotiate authentication to a server with

user1:password1 and then does another operation to the same server asking

for any authentication method but for user2:password2 (while the previous

connection is still alive) - the second request gets confused and wrongly

reuses the same connection and sends the new request over that connection

thinking it uses a mix of user1's and user2's credentials when it is in fact

still using the connection authenticated for user1...

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality low, integrity high, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: High — the attacker first has to win a race, learn a secret or otherwise prepare the target.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: Low — limited, and the attacker does not choose what is affected.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: None.

Weakness class

CVE-2026-5545 is classified as CWE-613: Insufficient Session Expiration. Sessions stay valid longer than they should, so an old identifier still grants access.

Affected software

CVE-2026-5545 is recorded against 1 package.

  • curl (from 7.10.6 up to 8.20.0)

Timeline and source

Published on 13 May 2026 and last revised on 17 June 2026. A public exploit is known to exist, which raises the urgency of patching considerably. A vendor advisory or fix has been published. Record sourced from NVD.

References

curl.se
curl.se
hackerone.com
hackerone.com

Other advisories for this package

curl has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-613: Insufficient Session Expiration) in other software:

Details

Severity MEDIUM
CVSS Score 6.5
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N
CWE CWE-613
Public Exploit ⚠️ Yes
Source NVD
Published 2026-05-13
Updated 2026-08-20
Modified 2026-06-17

Affected Packages

Software From version Fixed in
curl 7.10.6 8.20.0

References

Exploit, Issue Tracking, Third Party Advisory https://hackerone.com/reports/3642555
Exploit, Issue Tracking, Third Party Advisory https://hackerone.com/reports/3642555

Exploit Protection

Are you running curl?

CVE-2026-5545 carries CVSS 6.5 Medium rating and a public exploit already exists. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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